Turbo-machinery engines, such as combustion turbine engines, contain rotating blades in a compressor section and rotating blades in a turbine section. The blades are generally arranged circumferentially in rows with each row being comprised of a plurality of blades. Typical geometries include free standing blades (i.e. blades that do not contact adjacent blades) or shrouded blades (i.e. blades that do contact adjacent blades).
During normal engine operation, the rotating blades are exposed to excitation due to dynamic conditions in the engine such as flow induced vibration and nozzle effects. These dynamic conditions can lead to blade vibration, which is an appreciable cause of excitation failure in turbo-machinery.
A known means to avoid excitation failure is by monitoring operating blade vibration using a combination of strain gauges, non-contact capacitance probes, magnetic, or optical probes to measure the vibration. However, such monitoring and evaluation is both costly and time inefficient.
Another known method involves a target on top of a blade shroud. However, these painted targets are problematic because they cannot detect motion in all directions. More specifically, blade tip motion torsional to the detecting edges of the target cannot be discerned.
Although several techniques exist for vibration measurements of rotating bladed-disk assemblies, no technique provides a suitable description of the dynamic behaviour. Therefore, there exists a need in the field of technology of turbo-machinery for a method and device that can accurately, easily, and/or efficiently measure and monitor rotating blade torsional vibration.